Plate-fin heat exchangers or recuperators have been used to pre-heat combustion-inlet air in a microturbine. A typical configuration for a heat exchanger includes a stacked array of cells of plate-fins, each cell including top and bottom plates, an internal finned member or matrix fin disposed between the plates, two external finned members on the outside surfaces of the cell, an inlet header finned member, and an outlet header finned member. The header finned members and matrix finned members are typically brazed or otherwise metallurgically bonded to the top and bottom plates. The inlet and outlet header finned members are also commonly referred to as crossflow headers because they are positioned at the inlet and outlet ends of the cell and because the flow of fluid through them is at an angle with respect to the flow of fluid through the matrix finned member.
In some applications, the pressure in the headers can reach high levels, which forces the top and bottom plates away from each other and creates tension in the header finned members. The header finned members thus perform a structural function as they tie the top and bottom plates together and resist deformation of the header portion of the cell that may be caused by the pressure in the cell. Accordingly, the header finned members must be sufficiently strong to resist such tensile deformation.
While the header finned members must perform the above-described structural function, the header finned members must also be constructed to not unduly restrict flow of air. The density of the fins must be selected to minimize the pressure drop through the headers. A balance must be found between maximizing header fin density to provide structural strength to the header, and minimizing header fin density to lower the pressure drop across the header.
One known method for balancing the structural and performance requirements of a header is to make the header wide enough to provide sufficient fin density to meet structural requirements while allowing enough flow area to meet pressure loss or performance requirements. To minimize the cost of tooling, standard header sizes have been implemented to cover a range of applications. Problems arise with these standard head sizes when volumetric constraints, non-typical operating conditions, or unusual performance specifications are required for a particular application.